Current Biology, Volume 27 Supplemental Information Transcranial Direct Current Stimulation Facilitates Associative Learning and Alters Functional Connectivity in the Primate Brain Matthew R. Krause, Theodoros P. Zanos, Bennett A. Csorba, Praveen K. Pilly, Jaehoon Choe, Matthew E. Phillips, Abhishek Datta, and Christopher C. Pack
1..75 Field Strength (V/m).5.25 Figure S1. Electric field maps. A finite element model of each monkey s head was generated from structural MRIs and intraoperative records. It was then solved for electrode positions that maximize current flow through a specified brain area. In this example, we sought to maximize current flow through monkey M s PFC (grey square), for the experiment in Figure 1 and Figure 2A. Colors indicate the strength of the induced field, arrows indicate the current s direction. For additional details, see [S1], as well as the Results and Methods section.
19 18 17 16 Pupil Area (arbitrary units) 15 14 13 12 11 n.s. Baseline Ramp Steady State Trial Epoch Figure S2. Stimulation causes only transient changes in pupil area. Pupil area trajectories are shown for epochs before the onset of stimulation ( baseline ), while stimulation current is ramped up ( ramp ) and once current reaches its steady state of 2 ma, in blocks, or ma in sham blocks ( steady state ). Visual stimulation is held constant across all three epochs. Pupil area is significantly increased during the ramp phase, relative to the baseline, but returns to baseline once the current reaches steady state. Asterisks indicate p<.1 (see main text for details and numbers). Color indicates stimulation/sham condition (no significant difference between baseline and steady state was observed). Error bars indicate the standard error of the grand mean.
1 PFC 1 ITC Average LFP Power (µv 2 ) 1 1 1 Significant difference (p<.5; corrected) Average LFP Power (µv 2 ) 1 1 1 No pairs significantly differ Θ α β γ low Θ α β γ low Figure S3. increases LFP spectral power in PFC during behavior. Main Figure 4 shows the change in LFP power with stimulation. Here, we plot the average values for both and sham conditions within one monkey. indicates pairwise differences that are significant at a corrected.5 level (via randomized F tests). See main text and Main Figure 4 for details; color indicates stimulation condition, while error bars indicate the standard error of the grand mean.
A.25 PFC B.25 ITC Change in Coherence with.2.15.1.5 Change in Coherence with.2.15.1.5 Significant difference (p<.5; corrected) No significant differences (p>.5; corrected) -.5 Θ α β γ low Frequency Band -.5 Θ α β γ low Frequency Band Figure S4. alters functional connectivity within the stimulated areas. The difference between LFP-LFP coherence for and sham conditions within each array (see also Main Figure 6, which compares data across areas). Positive values indicate greater coherence during ; negative values indicate greater coherence during sham sessions, and error bars indicate the standard error of the difference of the grand means for each condition. When was applied, coherence significantly increased in all frequency bands in PFC ( denotes p <.5, corrected). However, no significant changes were observed in ITC in any frequency bands. See Main Figure 6 for coherence between areas.
.6.5 Average Coherence.4.3.2.1 Significant difference (p<.5; corrected) Θ α β γ low Figure S5. alters functional connectivity between brain areas. Main Figure 6 shows the change in LFP-LFP coherence between PFC and ITC with stimulation. Here we plot the average vales for each condition. indicates pairwise differences that are significant at a corrected.5 level, while error bars denote the standard error of the grand mean. See main text and Figure 6 for details
Supplemental Reference [S1]. Datta, A., Krause, M.R., Pilly, P.K., Choe, J., Zanos, T.P., Thomas, C., and Pack, C.C. (216). On comparing in vivo intracranial recordings in non-human primates to predictions of optimized transcranial electrical stimulation. Proceedings of the 38th Annual International Conference of the IEEE Engineering in Medicine and Biology Society.